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A critical role for hemolysin in Vibrio fluvialis-induced IL-1β secretion mediated by the NLRP3 inflammasome in macrophages.

Song L, Huang Y, Zhao M, Wang Z, Wang S, Sun H, Kan B, Meng G, Liang W, Ren Z - Front Microbiol (2015)

Bottom Line: The mice treated with 10(8) CFU wild-type V. fluvialis or cell-free supernatant containing VFH induced significantly higher IL-1β production in peritoneal lavage fluid or in colon compared with those infected with the mutant strain, while no effect on TNF and IL-6 production was observed at day 5 or 24 h post-infection.VFH has no effect on the synthesis of pro-IL-1β, but rather it triggers the processing of pro-IL-1β into IL-1β.Summary Sentence: Vibrio fluvialis-secreted hemolysin induces IL-1β secretion through the activation of the NLRP3 inflammasome and contributes to the pathogenicity of V. fluvialis.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention - Chinese Center for Disease Control and Prevention Beijing, China.

ABSTRACT
Vibrio fluvialis causes human diarrhea, but the pathogenesis is not well-studied. We hypothesized that V. fluvialis-secreted hemolysin (VFH) may induce IL-1β secretion through the activation of the NLRP3 inflammasome and contribute to the pathogenicity of V. fluvialis. To examine this possibility, we constructed VFH mutant and complement strains and demonstrated that V. fluvialis-induced IL-1β production and cytotoxicity in human monocytic THP-1 cells and mouse macrophages is attributed to VFH. To evaluate the role of VFH in vivo, we infected adult C57BL/6 mice intraperitoneally and suckling C57/B6 mice orally with various strains. The mice treated with 10(8) CFU wild-type V. fluvialis or cell-free supernatant containing VFH induced significantly higher IL-1β production in peritoneal lavage fluid or in colon compared with those infected with the mutant strain, while no effect on TNF and IL-6 production was observed at day 5 or 24 h post-infection. VFH contributed to pathological changes and IL-1β release independent of colonization of V. fluvialis in the colon. VFH has no effect on the synthesis of pro-IL-1β, but rather it triggers the processing of pro-IL-1β into IL-1β. Furthermore, using deficient mouse strains, we verified that V. fluvialis-induced IL-1β is mediated through activation of Caspase-1 and the NLRP3 inflammasome ex vivo. Confocal microscopy suggests that VFH contributes to cathepsin B release. Furthermore, V. fluvialis-induced IL-1β secretion requires potassium (K(+)) efflux and reactive oxygen species production. Our results provide new evidence for the role of VFH in the activation of the NLRP3 inflammasome and pathogenesis in response to V. fluvialis infection. Summary Sentence: Vibrio fluvialis-secreted hemolysin induces IL-1β secretion through the activation of the NLRP3 inflammasome and contributes to the pathogenicity of V. fluvialis.

No MeSH data available.


Related in: MedlinePlus

Vibrio fluvialis-secreted hemolysin triggers IL-1β production and cytotoxicity in vivo. (A,C,E) C57BL/6 mice were injected i.p. with PBS as control or 108 CFU WT, Δvfh, or pUC-vfh. Mice (n = 6) were sacrificed 5 days after injection, and the IL-1β (A), TNF (C) and IL-6 (E) in PLF was measured by ELISA. (B,D,F) Five-days-old sucking mice were infected orally with PBS as a control or 108 CFU WT, Δvfh, or pUC-vfh. Mice (n = 6) were sacrificed 24 h p.i. and the ileum and colon were homogenized. The production of IL-1β (B), TNF (D) and IL-6 (F) in homogenate was assayed by ELISA. (G) Five-days-old sucking mice (n = 6) were treated by gavage with cell-free supernatant from overnight culture of various strains. The level of IL-1β, TNF, and IL-6 in homogenates of colon at 24 h p.i. were measured by ELISA. (H) The V. fluvialis colonization in ileum and colon was quantified by plating the diluted homogenates on LB plates containing 50 μg/ml streptomycin. Results represent the mean + SD of triplicates. ∗P < 0.05; ∗∗P < 0.01.
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Figure 3: Vibrio fluvialis-secreted hemolysin triggers IL-1β production and cytotoxicity in vivo. (A,C,E) C57BL/6 mice were injected i.p. with PBS as control or 108 CFU WT, Δvfh, or pUC-vfh. Mice (n = 6) were sacrificed 5 days after injection, and the IL-1β (A), TNF (C) and IL-6 (E) in PLF was measured by ELISA. (B,D,F) Five-days-old sucking mice were infected orally with PBS as a control or 108 CFU WT, Δvfh, or pUC-vfh. Mice (n = 6) were sacrificed 24 h p.i. and the ileum and colon were homogenized. The production of IL-1β (B), TNF (D) and IL-6 (F) in homogenate was assayed by ELISA. (G) Five-days-old sucking mice (n = 6) were treated by gavage with cell-free supernatant from overnight culture of various strains. The level of IL-1β, TNF, and IL-6 in homogenates of colon at 24 h p.i. were measured by ELISA. (H) The V. fluvialis colonization in ileum and colon was quantified by plating the diluted homogenates on LB plates containing 50 μg/ml streptomycin. Results represent the mean + SD of triplicates. ∗P < 0.05; ∗∗P < 0.01.

Mentions: To evaluate the role of VFH in inflammatory response, bacterial colonization, and pathology change induced by V. fluvialis in vivo, we infected adult mice i.p. with 108 CFU WT, Δvfh, and pUC-vfh strains and measured the cytokines in PLF at day 5 p.i. The mice injected with WT and pUC-vfh strains induced significantly more IL-1β than those injected with Δvfh (Figure 3A). The VFH-dependent IL-1β induction was confirmed in colon using a suckling mouse model (Figure 3B). In contrast to the results for IL-1β, no difference among the strains was observed for TNF-α (Figures 3C,D) or IL-6 (Figures 3E,F).


A critical role for hemolysin in Vibrio fluvialis-induced IL-1β secretion mediated by the NLRP3 inflammasome in macrophages.

Song L, Huang Y, Zhao M, Wang Z, Wang S, Sun H, Kan B, Meng G, Liang W, Ren Z - Front Microbiol (2015)

Vibrio fluvialis-secreted hemolysin triggers IL-1β production and cytotoxicity in vivo. (A,C,E) C57BL/6 mice were injected i.p. with PBS as control or 108 CFU WT, Δvfh, or pUC-vfh. Mice (n = 6) were sacrificed 5 days after injection, and the IL-1β (A), TNF (C) and IL-6 (E) in PLF was measured by ELISA. (B,D,F) Five-days-old sucking mice were infected orally with PBS as a control or 108 CFU WT, Δvfh, or pUC-vfh. Mice (n = 6) were sacrificed 24 h p.i. and the ileum and colon were homogenized. The production of IL-1β (B), TNF (D) and IL-6 (F) in homogenate was assayed by ELISA. (G) Five-days-old sucking mice (n = 6) were treated by gavage with cell-free supernatant from overnight culture of various strains. The level of IL-1β, TNF, and IL-6 in homogenates of colon at 24 h p.i. were measured by ELISA. (H) The V. fluvialis colonization in ileum and colon was quantified by plating the diluted homogenates on LB plates containing 50 μg/ml streptomycin. Results represent the mean + SD of triplicates. ∗P < 0.05; ∗∗P < 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440915&req=5

Figure 3: Vibrio fluvialis-secreted hemolysin triggers IL-1β production and cytotoxicity in vivo. (A,C,E) C57BL/6 mice were injected i.p. with PBS as control or 108 CFU WT, Δvfh, or pUC-vfh. Mice (n = 6) were sacrificed 5 days after injection, and the IL-1β (A), TNF (C) and IL-6 (E) in PLF was measured by ELISA. (B,D,F) Five-days-old sucking mice were infected orally with PBS as a control or 108 CFU WT, Δvfh, or pUC-vfh. Mice (n = 6) were sacrificed 24 h p.i. and the ileum and colon were homogenized. The production of IL-1β (B), TNF (D) and IL-6 (F) in homogenate was assayed by ELISA. (G) Five-days-old sucking mice (n = 6) were treated by gavage with cell-free supernatant from overnight culture of various strains. The level of IL-1β, TNF, and IL-6 in homogenates of colon at 24 h p.i. were measured by ELISA. (H) The V. fluvialis colonization in ileum and colon was quantified by plating the diluted homogenates on LB plates containing 50 μg/ml streptomycin. Results represent the mean + SD of triplicates. ∗P < 0.05; ∗∗P < 0.01.
Mentions: To evaluate the role of VFH in inflammatory response, bacterial colonization, and pathology change induced by V. fluvialis in vivo, we infected adult mice i.p. with 108 CFU WT, Δvfh, and pUC-vfh strains and measured the cytokines in PLF at day 5 p.i. The mice injected with WT and pUC-vfh strains induced significantly more IL-1β than those injected with Δvfh (Figure 3A). The VFH-dependent IL-1β induction was confirmed in colon using a suckling mouse model (Figure 3B). In contrast to the results for IL-1β, no difference among the strains was observed for TNF-α (Figures 3C,D) or IL-6 (Figures 3E,F).

Bottom Line: The mice treated with 10(8) CFU wild-type V. fluvialis or cell-free supernatant containing VFH induced significantly higher IL-1β production in peritoneal lavage fluid or in colon compared with those infected with the mutant strain, while no effect on TNF and IL-6 production was observed at day 5 or 24 h post-infection.VFH has no effect on the synthesis of pro-IL-1β, but rather it triggers the processing of pro-IL-1β into IL-1β.Summary Sentence: Vibrio fluvialis-secreted hemolysin induces IL-1β secretion through the activation of the NLRP3 inflammasome and contributes to the pathogenicity of V. fluvialis.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention - Chinese Center for Disease Control and Prevention Beijing, China.

ABSTRACT
Vibrio fluvialis causes human diarrhea, but the pathogenesis is not well-studied. We hypothesized that V. fluvialis-secreted hemolysin (VFH) may induce IL-1β secretion through the activation of the NLRP3 inflammasome and contribute to the pathogenicity of V. fluvialis. To examine this possibility, we constructed VFH mutant and complement strains and demonstrated that V. fluvialis-induced IL-1β production and cytotoxicity in human monocytic THP-1 cells and mouse macrophages is attributed to VFH. To evaluate the role of VFH in vivo, we infected adult C57BL/6 mice intraperitoneally and suckling C57/B6 mice orally with various strains. The mice treated with 10(8) CFU wild-type V. fluvialis or cell-free supernatant containing VFH induced significantly higher IL-1β production in peritoneal lavage fluid or in colon compared with those infected with the mutant strain, while no effect on TNF and IL-6 production was observed at day 5 or 24 h post-infection. VFH contributed to pathological changes and IL-1β release independent of colonization of V. fluvialis in the colon. VFH has no effect on the synthesis of pro-IL-1β, but rather it triggers the processing of pro-IL-1β into IL-1β. Furthermore, using deficient mouse strains, we verified that V. fluvialis-induced IL-1β is mediated through activation of Caspase-1 and the NLRP3 inflammasome ex vivo. Confocal microscopy suggests that VFH contributes to cathepsin B release. Furthermore, V. fluvialis-induced IL-1β secretion requires potassium (K(+)) efflux and reactive oxygen species production. Our results provide new evidence for the role of VFH in the activation of the NLRP3 inflammasome and pathogenesis in response to V. fluvialis infection. Summary Sentence: Vibrio fluvialis-secreted hemolysin induces IL-1β secretion through the activation of the NLRP3 inflammasome and contributes to the pathogenicity of V. fluvialis.

No MeSH data available.


Related in: MedlinePlus